What Is HDR?

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HDR is short for High Dynamic Range Imaging, actually HDRI, but HDR is typically what you see in the industry and around the web. So what exactly is High Dynamic Range Imaging? It is the process of combining multiple exposures of a scene to create one image that displays all of the luminance information gathered in the multiple exposures.

The exposures are processed using software specifically designed for HDR processing. The current HDR software leaders are Photomatix Pro and HDR Efex Pro. A process called tone mapping is required to translate the processed HDR image into a usable 8 bit (.jpg) or 16 bit (.tif) image. During the tone mapping phase you have complete control over the contrast, detail, saturation, and luminosity to mention a few. Here is a great resource to dive further into the numbers and math behind the inner workings of high dynamic range.

If you are a photographer already you are probably thinking, “Alright I’m getting it”, while the average Joe is thinking, “You had me at HDR is short for what?” Here is an example for you:

Have you ever been breath taken by a beautiful sunset over the ocean, so moved by its beauty that you took out any device that could possible capture its magnificence? Awe inspired by its glamor you can’t wait to get home and look at it on your monitor. The anticipation of possibly seeing it once again is tugging on your heart strings, your mouth is watering as you plug your camera into your computer. The window pops up, “What would you like to do with this removable storage device”. You are thinking, “Anything computer, do anything with it just show me the magnificently contrasted, beautifully colored, well composed epic photograph that so mystically captivated my soul and just may possibly be the bane of my existence!”

And…..

There it is, the washed out low contrast, image of an ugly ocean and its incompatible sunset. The reds look like half breed cousins of the awful orange next door. Instead of the vibrant cyan sea foam coated ocean, you are left with moody blues. Your lively dancing greens appear to be taking the day off showing you their muddy backsides. Your image is not as you saw it, you try to imagine that it is by showing it off, thinking maybe someone will see it like I did, but their expression doesn’t seem to capture an ounce of the awe inspired sunset juice that recently passed through your heart.

This my friends is where HDR comes right in to save the day and swoop you off your feet. Check out the variations below:

You can see that by taking 5 separate photographs and manipulating the amount of contrast, saturation, detail, and luminosity you can achieve a more accurate depiction of the vibrant scene that you recently saw. The image on the left is straight out of the camera, no editing, as you can see I didn’t even straighten the horizon! The second picture shows you more of what I actually saw, but I needed the HDR process to achieve the finished image.

3 Comments

Mohit Khanna
on July 27, 2011 at 3:23 am

Hi,

In almost all of the HDR tutorials I have read online, the HDR pics are created from 5 exposure images. As is the case in the sunset image above.

Can you help me understand as to what level of detail would be missing in the case of only 3 exposure levels (most DSLRs support only 3 auto-bracketed images). Can it be compensated by post-processing?

As I do not own a DSLR yet, this aspect is making the decision a bit more tough for me. Have you ever given Nikon D7000 a try? How’re the HDR images from that one?

Is it possible to show the same HDR pic created with 3 as well as 5 exposure levels?

That is a big question in a sense. HDR images rely heavily on the Exposure Value at which you take the exposures. When you take the exposures +/-1 EV should be your Auto Exposure Bracket of choice. This allows double the amount of light (+1) and half of the amount of light (-1) in per exposure of the bracket. A 3 exposure bracket would give you 3 exposures that look something like this -1,0,+1 EV. While you will get a difference in contrast with three exposures, the extra 2 exposures make a world of difference with -2,-1,0, +1, +2. The extra +1 EV exposure gives you dramatic highlights where the shadows have almost gone into a 50% grey, the -2 EV gives you dramatic shadow where the highlights have gone into a 50% grey. There is very valuable shadow and highlight information in those 2 extra exposures. I prefer 5 exposure HDRs because you can push them a little bit further in the tonemapping stage, because that information is present you can push the slider bars and extra couple of millimeters without disturbing the image.

However, you can “fake” the exposures in Photoshop, “Pseudo” HDR using the Exposure adjustment layer. Simply slide it up 1, save it as +1, slide it up 2, save as +2 and repeat for -1, and -2. These Pseudo’s do not create the greatest HDR’s but will get the job done in a pinch. You can also tonemap a single Raw file and get great results, not as great as a 5 exposure HDR but still great.

I will be sure to email you when it is done.

I have never shot with the Nikon D7000, I am an Olympus guy and love my E-30. IT is relatively inexpensive and for the price you get a killer 5 exposure AEB. I explain all of this in great detail in the book I am writing. I will be sure to email you when it is done.

How do images created by cameras that have an HDR function compare with HDR images created in post-processing? Is it worth buying a camera that does HDR, or should one just do the exposure bracketing on a number of images and combine them in post-process for a better image? Is the effect the same?

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